Compensated gate circuit



Nov. 25, 1958 e. c. SUMMERS COMPENSATED GATE CIRCUIT Filed Aug. 8, 1956 GERA L 0 6f SUMMERS INVENTOR.

A TTORNE Y States nite COMPENSATED GATE CIRCUIT Application August 8, 1956, Serial No. 602,806

6 Claims. (Cl. 250-27) This invention relates to electronic gates and more particularly to a compensated electronic gate in which switching transients are eliminated. In many applications it is common to pass pulses through electronic gates which, when the gate is closed, will not reach succeeding circuits but when the gate is open, permit the pulses to pass on to the succeeding circuits. The present invention is an improvement over the gate circuit disclosed in Patent No. 2,597,796 to Hindall.

In accordance with the present invention there is provided a compensated gating circuit which has a diode connected to ground at the cathode thereof and connected at the anode thereof to the cathode of a normally conducting grid controlled vacuum tube, which tube may be made non-conducting by application of a switching pulse thereto. An impedance means is provided for applying pulses to the juncture between said diode and the cathode of said vacuum tube and for connecting said juncture to an output terminal. A load impedance connected at a first terminal thereof to the anode of the vacuum tube and to a voltage supply source at a second terminal thereof completes a D. C. path through the tube and diode. A compensating circuit connected between said first terminal and said output terminal has an impedance which is high compared to the impedance to ground from said output terminal for application of a voltage to said output terminal which concomitantly varies the potential level at said output terminal in such a way as to oppose the changes which occur when conductivity of said vacuum tube is varied.

For further objects and advantages of the invention and for a more complete understanding thereof, reference may now be had to the following description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a circuit diagram of the present invention; and

Fig. 2 is a graph of voltages at various points in the circuit of Fig. 1 as pulses are applied thereto.

Referring to Fig. 1, there is provided a system in which signals from a source 10 selectively are to be passed to an output circuit including output impedance 11. The upper terminal of source 10 is connected by way of a pair of resistances 12 and 13, connected in series, to output terminal 14 and to the upper end of output resistance 11. The lower terminals of source 10 and resistance 11 are connected to ground. A diode 16 is connected at its anode 17 to the juncture intermediate resistors 12 and 13 and is connected at its cathode 18 to ground. A vacuum tube such as a triode 20 is connected at its cathode to the juncture 19. The anode of tube 20 is connected by way of load resistor 21 to the positive terminal of a source 22 of plate supply. The control grid of tube 20 is connected by way of resistor 23 to a source of positive potential such as the anode supply 22.

In accordance with the present invention, an additional circuit is provided including a condenser 25 and a resistor 26 connected in series between the anode of tube 20 and Patented Nov. 25, 1958 2 the output terminal 14. By providing the latter circuit, variations in the potential at the output terminal 14 as may be caused by switching transients may be eliminated.

In operation a series of pulses 30 are applied to the circuit from source 10. It is desired to permit only those pulses such as appear during the interval of a control pulse 31 to be passed to the output terminal 14-. At the same time it is desirable that no additional transients or pulses appear at the output terminal 14 by reason of switching transients introduced by the beginning and the end of negative gating waveform 31.

During the interval 32 tube 20 is conducting by reason of the positive voltage on its grid so that a relatively large anode current flows through battery 22 and through diode 16. When the diode 16 is conducting, its impedance is very low, of the order of 300 ohms, for units such as are presently available. If resistors 12 and 13 are made relatively large, for example in the order of 33,000 ohms, then the diode 16 effectively shunts the pulses during interval 32 so that they do not appear across output impedance 11. However, when control gate 31 is applied to the grid of tube 20, the current flow through tube 20 is terminated and the negative portions of the pulses 30 appearing during interval 31 will then be transmitted without substantial attenuation to output terminal 14 and will appear across resistor 11. The positive half of the latter pulses however are shunted effectively by reason of the low forward impedance of the diode 16.

The abrupt change in the conductivity of tube 20 coincident with the onset of gate waveform 31 ordinarily will produce a transient in the cathode of tube 19 which would, unless compensated, appear at the output terminal 14. More particularly, the flow of anode current from tube 20 through the diode having a relatively low resistance ordinarily would produce a voltage at the cathode of about 5 volts relative to ground. The latter voltage, of course, will depend upon the magnitude of the current flow through tube 20. When the latter current is terminated by application of waveform 31, the cathode of tube 20 tends to seek ground level generally as shown by line graph 40, Fig. 2. At the same time the voltage at the anode of tube 20 rises abruptly to the value of battery 22 as shown by line graph 41. By provision of the circuit including condenser 25 and resistor 26, a voltage opposite in sense to the change in cathode voltage is applied to terminal 14 so that as the cathode of tube 19 approaches ground, thus tending to lower the potential of point 14, an equal and opposite voltage derived from the anode of tube 20 as the latter voltage rises is applied to point 14 to maintain point 14 at a constant potential. The latter voltage, i. e., a portion of the anode voltage, is shown by line graph 42. Thus only voltage changes due to the pulses 30 which appear or occur in the interval spanned by pulse 31 will be transmitted through the output condenser 27 to succeeding circuits.

In a modification of the invention, the condenser 25 may be eliminated whereupon a relatively small current flowing through resistors 26, 13 and 12 would result in a slightly diiferent voltage at point 14, but potential at point 14 may be maintained constant during application of a switching gate 31 to the tube 20.

A small condenser 28 connected in parallel with resistor 26 may be used to compensate for very sharp transients at the switching instants. Adjustment preferably will be made in the size of this condenser to optimize performance for the complete elimination of switching transients. Condenser 28 preferably will have an impedance which in general bears approximately the same ratio to the stray capacity to ground of the circuit as viewed from point 14 as resistor 26 bears to the sum of resistors 12 and 13.

I 2,862,104.- l A 3 The stray or shunt capacity may be of the order of 50 or 60 mieromicrofarads, the specific value being in general different for each circuit. In the present case, as shown below, the ratio of Therefore condenser 28 would be of the order of one or two micromicrofarads.

In one embodiment of the invention, circuit components with the following values and types were used:

Diode 16 6BQ7 (V2 diode connected). Triode 20 6BQ7 /2).

Resistors 12 and 13 33,000 ohms.

Resistor 11 3.9 megohms.

Resistor 21 27,000 ohms.

Resistor 23 1 megohm.

Resistor 26 3.9 megohms.

Condenser 28 1-5 or 6 micromicrofarads. Battery 22 270 v.

While the invention has been described in connection with certain specific embodiments thereof, it is to be understood that further modifications may now suggest themselves to those skilled in the art and it is intended to cover such modifications as fall within the scope of the appended claims.

What is claimed is:

1. In a gating circuit having a diode connected to ground at the cathode thereof and at the anode thereof to the o cathode of a normally conducting grid controlled vacuum tube the improvement which comprises impedance means for applying signals to the juncture between said diode and the cathode of said vacuum tube, an impedance for connecting said juncture to an output terminal, a load impedance connected at a first terminal thereof to the anode of said vacuum tube, a voltage supply source connected to the second terminal of said load impedance, and means for applying fractional portions of voltage changes appearing at the anode of said vacuum tube to said output terminal to oppose the change which appears across said diode when conductivity of said vacuum tube is varied.

2. A controlled path for signals from a signal source comprising a series circuit connected to said source including an impedance and a diode connected at its anode to said impedance, an output terminal, an output circuit including an impedance interconnecting said anode and said output terminal, a source of direct current having the negative terminal thereof connected to ground, a current path connected to the positive terminal of said source and including in series an anode impedance and a normally conducting vacuum tube connected at its anode to said anode impedance and at its cathode to the anode of said diode, means for selectively rendering said vacuum tube non-conductive for passage of signals from @id source to said output terminal, and means for applying fractional portions of voltage at the anode of said vacuum tube to said output terminal to maintain said output terminal at a uniform average voltage as conductivity of said vacuum tube is varied.

3. A controlled path for signals from a signal source comprising a series circuit connected to said source including an impedance and a diode connected at its anode to said impedance, an output terminal, an output circuit including an impedance interconnecting said anode and said output terminal, a source of direct current having the negative terminal thereof connected to ground, a current path connected to the positive terminal of said source and including in series an anode impedance and a normally conducting vacuum tube connected at its anode to said anode impedance and at its cathode to the anode of said diode, means for selectively rendering said vacuum tube non-conductive for passage of signals from said source to said output terminal, and means for maintaining said output terminal at a uniform average voltage comprising a path connected in parallel to said vacuum tube comprising impedance means interconnecting the anode thereof and said output terminal, which impedance means bears the same ratio with respect to the sum of the impedances connected to the anode of said diode as the voltage across said anode impedance bears to the voltage across said diode.

4. The combination set forth in claim 3 in which said last named impedance means comprises a resistance and a condenser connected in parallel wherein said condenser has a capacity which bears the same relationship to the stray capacity appearing between the anode of said diode and ground as said resistance means bears to the sum of the impedances connected to the anode of said diode.

5. In a circuit for controlling transmission of signals from a signal source to an output terminal which circuit has a diode connected to ground at the cathode thereof and at the anode thereof to the cathode of a normally conducting grid controlled vacuum tube, the improvement which comprises an impedance interconnecting said source and said output terminal and connected at a midpoint thereof to the juncture between said diode and the cathode of said vacuum tube, a resistor connected at a first terminal thereof to the anode of said vacuum tube, a voltage supply source connected to the second terminal of said resistor, and a series circuit interconnecting the anode of said vacuum tube and said output terminal comprising a blocking condenser and a resistor which is large compared to said impedance for applying fractional portions of voltage changes appearing at the anode of said vacuum tube to said output terminal to oppose the change which appears across said diode when conductivity of said vacuum tube is varied.

6. In a circuit controlling transmission of signals from a signal source to an output terminal which has a diode connected to ground at the cathode thereof and at the anode thereof to the cathode of a normally conducting grid controlled vacuum tube the improvement which comprises a series resistor interconnecting said source and said output terminal and connected at a midpoint to the juncture between said diode and the cathode of said vacuum tube, a load impedance connected at a first terminal thereof to the anode of said vacuum tube, a voltage supply source connected to the second terminal of said load impedance, and means including a resistor interconnecting the anode of said vacuum tube and said output terminal wherein said resistance has a value which with respect to said series resistor is the same as the sum of said load impedance and the anode-cathode impedance of said vacuum tube, when conducting, is to the anode-cathode impedance of said diode, when conducting, for applying fractional portions of voltage changes appearing at the anode of said vacuum tube to said output terminal to oppose the change which appears across said diode when conductivity of said vacuum tube is varied.

References Cited in the file of this patent UNITED STATES PATENTS 

